Field of the Invention
This invention relates to an electrically powered vehicle, and particularly to an electrically powered vehicle including a gear type transmission in an electric power transmission path between a rotation shaft of a motor and drive wheels.
Description of the Background Art
Japanese Patent Laying-Open No. 2007-112349 discloses a hybrid power unit distributing output from an internal combustion engine to a generator and a rotation output shaft and transmitting output from a motor to the rotation output shaft through a transmission. In this hybrid power unit, shift shock is lessened by reducing torque of the motor during gear shifting in the transmission and an amount of generation of electric power by the generator is decreased by reducing torque of the generator in order to hold power balance of a battery.
According to this hybrid power unit, since output from the internal combustion engine is not lowered during gear shifting in the transmission, shift shock can appropriately be lessened without generating response delay in output rotation (see Japanese Patent Laying-Open No 2007-112349).
During gear shifting in a gear type transmission, change in rotation of an input shaft of the transmission is abrupt, and in order to shift a gear with shift shock being suppressed, output (torque and power) from a motor coupled to the input shaft of the transmission should suddenly be changed. Basically, the motor is controlled such that electric power input to and output from an electric power storage device such as a battery does not exceed an allowable value (allowable output electric power Wout and allowable input electric power Win), however, electric power input to and output from the electric power storage device may exceed the allowable value due to delay in a control system. Namely, due to delay caused by communication or delay caused by filtering processing, delay in effectuation of a calculated instruction actually takes place, and electric power input to and output from the electric power storage device may exceed the allowable value under the influence of this delay in effectuation. Such delay in effectuation always takes place regardless of whether or not a gear is being shifted, however, it becomes noticeable when it affects excess of electric power input to and output from the electric power storage device during gear shilling in which output from the motor is suddenly changed. Excess of electric power input to and output from the electric power storage device over an allowable value leads to deterioration of the electric power storage device.
In a case that a voltage converter is provided between a drive device such as an inverter driving a motor and an electric power storage device, when power of the motor is changed, electric power is input to and output from a capacitor provided between the voltage converter and the drive device. In order to suppress fluctuation in voltage of the capacitor caused by input and output of electric power, the voltage converter is actuated and electric power is input to and output from the electric power storage device. Here, when power of the motor is suddenly changed in order to shift the gear with shift shock being suppressed, for example, during gear shifting, electric power input to and output from the capacitor increases, and consequently, electric power input to and output from the electric power storage device may exceed an allowable value. As set forth above, such excess leads to deterioration of the electric power storage device.